Both are Obama supporters, and celebrities were a big part of his strategy to attract voters. Bruce Springsteen is a regular supporter, as is Lena Dunham, Scarlett Johansson, Jay-Z and dozens and dozens of others.
Pop-rock trio Fun., who had a wild year with two No 1 hits, a near-platinum album and six Grammy nominations, will perform for First Lady Michelle Obama and her daughters Sasha and Malia, and Vive-President Joe Biden's wife, Jill, today at the Kids' Inaugural Ball.
"It's been amazing year, and 2013 is kicking off with us doing the inauguration ... it's just an incredible thing," said lead singer Nate Ruess. "I think the three of us care so much about Obama and so to be invited, I can't even deal."
Fun. will be joined by Perry, Wonder, Keys, Usher, Smokey Robinson, Paisley, Marc Anthony, Mindless Behavior, Nick Cannon and the cast of Glee.
"I think they're all very talented people. Stevie's my brother and so is Usher," Robinson said. "I know Katy ... I'm very happy to be performing among them."
While there will be no shortage of star power, it's not quite a repeat of the 2009 inauguration, when everyone who's anyone flocked to Washington for a televised concert on the Mall.
The first time around, Beyonce was a surprise guest, singing the Etta James classic At Last.